Heat exchangers, or heat extractors, are typically mounted on heat generating or heat transporting articles, such as a section of stovepipe or are inserted into the article. When used in conjunction with a stovepipe, they attempt to improve energy efficiency of a stove or fireplace system by increasing the distribution of heat to the surrounding room area. A typical exchanger for such applications utilizes transverse pipes arranged across an enclosed box that is inserted in the length of stovepipe so that flue gases enter the box and flow about the exterior of the pipes. Room air is blown through the pipes for heat exchange purposes (a variation of this form of heat exchanger is shown in U.S. Pat. No. 4,235,286). An alternative is the use of multiple smoke tubes in place of the single stovepipe in one section above a stove (see U.S. Pat. No. 4,232,732). Blowers are also arranged between concentric cylinders about the exterior of a stovepipe to improve convection (see U.S. Pat. Nos. 1,631,721, 4,448,348 and 4,467,959). Heat exchangers have been criticized because of a common tendency to increase creosote accumulation in the stove system, which is due to their common property of cooling at least a portion of the stovepipe.
The general concept of attaching an exposed finned heat exchanger to the exterior of a water heater is shown in U.S. Pat. No. 2,161,417. A similar type of stovepipe heat exchanger that requires no modification of the stovepipe itself and involves the addition of exposed radiating fins mounted about the cylindrical stovepipe surfaces has been marketed for use with stoves. This prodict known as CHIMFIN (TM) radiators, has been manufactured by the Condar Company of Garrettsville, Ohio, and was shown in the Woodstove Fireplace and Equipment Directory (1979) at page 154. Both fin structures utilize relatively large metallic surfaces in direct contact with the heated cylindrical surfaces on which they are mounted. This covering structure substantially impedes normal radiation of heat from the covered areas and reduces overall efficiency. In addition, the CHIMFIN product is stated to be produced from aluminum having black fin surfaces that "emit maximum radiant heat." Since the fin surfaces are emissive, they also will absorb most radiation directed to these surfaces. This absorptive quality limits the transmission of heat to the surrounding atmosphere.
The present invention seeks to maintain most of the normal heat radiating capability available in an article such as a conventional stovepipe, while adding substantially to its conductive area and imparting novel reflective properties to dissipate radiant heat energy to the surrounding atmosphere. This has been done effectively without the use of forced air techniques--in fact, forcing air about the described heat exchanger has been found to destroy its effectiveness.
The present invention provides a nonintrusive heat exchanger that can be readily mounted about any cylindrical heated object or article. It requires no modification of the item with which it is used. It uniquely combines heat conduction and surface reflective qualities to substantially add to the quality of heat available for convection by normal room air currents.